The prior art solutions for driver wake-up devices have been either analyzing the infrared light reflection from the eye fundus or eyelid to detect the level of the driver's fatigue or analyzing the movements of driver's eyelashes, to generate the wake-up signals for drivers. To use eyelashes for analyzing the eye movements of the driver are too critical. Eyelashes are too whimsical for an optical system. Eyelashes can be dark, blond, thick or thin. Therefore none of these sleep preventing devices have been working, nor have been marketed so far in USA.
The present invention distinguish from these previous art solutions, in that the lightbeam according to the present invention is interrupted by the movements of the eyelid, instead for being interrupted by the movements of eyelashes.
The present invention is a sleep-preventing device for an autombile driver, for day- and night-time driving, generating an alarm signal, whenever the eyes of the driver have been closed for a longer time period than a second.
The present invention distinguish also from previous sleep prevention devices, because the positioning of the emitter is smoothly adjustable in tiny increments along the temple of the eyeglasses.
The present invention is different from previous driver-wake-up devices, because narrow-band emitter light is used and a narrow band filter is positioned in front of the photosensor, to prevent the ambient light from all the other frequencies from interfering with the optics of the sensing system, according to this invention.
The present invention distinguishes from previous inventions, because in electronic circuitry, instead of a regular resistor as a balancing circuit element for the photosensor, a cadmium-sulfide photocell (which has resistivity, which is decreasing with increased illumination) is used for eliminating the ambient light effect to the photocell circuitry.
In an other embodiment of this invention it is used a pulsating light source, in order to addittionally diminish the influence of ambient light variations to the optical system according to this invention.
For daytime driving, according to the present invention, this sleep-preventing device has to have an infrared light reflecting coating on the eyeglasses and a light shield mounted to an eyeglass temple, behind the emitter, to prevent direct sunlight from falling onto the photosensor.
It seems, that none of the previous inventors have proceeded into practical application of this sleep-preventing device, involving the influence of daylight and ambient light to the optical system of these sleep preventing devices.
The device, according to the current invention is working as designed and has been already reduced to practice for night-time and for day-time driving.
Some prior art solutions by other inventors, who are looking at the movements of the eyelashes, are as follows.
In U.S. Pat. No. 2,726,380, inventor H. A. Campisi states on lines 56 to 63 in the description of his invention: "The so-established collimated light beam developed by the light source is directed between the bow of the spectacles and the nosepiece so as to traverse a path close enough to the operator's eyes that the eyelashes, during winking or nictation, cause this light path to be eclipsed or intercepted and interrupt the light rays which otherwise would be directed into the light responsive cell." FIG. 1 of U.S. Pat. No. 2,726,380 shows the light beam being emitted from a light source and received by a photocell and intercepting eyelashes.
In U.S. Pat. No. 4,875,030 inventor Chio states, in his Detailed Descripion of Preferred Embodiments, on lines 25 to 33 "It should be noted a normal blink usually causes no more than 0.3 miliseconds of stay of the eyelashes at its lowest position where beam passes. Thus such a transient interruption of illumination on the photo-diode 2 does not cause any response. However, if the break of illumination exceeds the upper limit of time of a human's natural blink, the alarm device will be triggered to actuate the buzzer 3 to produce an acoustic alarm". Thus he says, that a longer stay of eyelashes at its lowest position where the beam passes eyelashes, gives alarm evidence and it produces an acoustic alarm.
In U.S. Pat. No. 4,144,5531 inventor Arnberger states in the Abstract of the Invention: A safety apparatus for detecting an individual becoming drowsy is provided comprising a wave emitter mounted on an eyeglasslike frame for emitting a wave along a path directed to pass close to the individual's eyeball without impinging the latter that said wave is interrupted by the eyelashes when the eyelid is quivering, and detecting means on the frame for generating a signal in response to the wave being interrupted". FIG. 2 in the same U.S. Pat. No. 4,144,531 shows the sensing light beam and shows the eyelashes of the driver's left eye interrupting that light beam.